JPH10130728A - Production of grain oriented silicon steel sheet excellent in low magnetic field characteristic compared to high magnetic field characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the core loss characteristics in the low magnetic field of a steel sheet by prescribing the producing conditions in hot rolling and hot rolled sheet annealing. SOLUTION: For obtaining low magnetic field characteristics particularly required for the iron core of a small generator or the like, until hot rolling, the state of AlN is held to solid solution. and, in the temp. rising stage in hot rolled sheet annealing, AlN is precipitated. Concretely, the inlet side temp. in finish hot rolling of a slab is regulated to >=900 deg.C, and the cumulative draft of four passes in the stage before hot rolling is regulated to >=90%. In this way, the precipitation of AlN in the process of the finish rolling does not occur, and its low magnetic field characteristics are made satisfactory. Next, the hot rolled coil in which the precipitation of AlN is suppressed is subjected to hot rolled sheet annealing, and, it is the point that the temp. range is regulated to 800 to 950 deg.C, which is the lower one compared to the conventional case. Namely, in the case the annealing temp. is less than 800 deg.C, the fine precipitation of AlN in the temp. rising stage is made insufficient, and in the case of >950 deg.C, the form of AlN deteriorates, and secondary recrystallization is made unstable to deteriorate its magnetic properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a grain-oriented electrical steel sheet used for an iron core of a transformer or a generator, and more particularly to an iron core of a small generator or an EI core, which is superior in a low magnetic field characteristic to a high magnetic field characteristic. The present invention relates to an advantageous method for producing a grain-oriented electrical steel sheet suitable for required applications.

[0002]

2. Description of the Related Art Si is contained and the crystal orientation is (110) 001
Oriented electrical steel sheets oriented in the orientation and the (100) 001 orientation are widely used as various iron core materials in the commercial frequency range because of their excellent soft magnetic properties. The characteristics required of this type of electromagnetic steel sheet include, in particular, iron loss (generally, W _17/50 (W / kg), which is the loss when magnetized to 1.7 T at a frequency of 50 Hz).
Is important.

[0003] In the iron core and wound iron core of a large transformer, a material having a low value of _{W17 / 50} has obtained a result that the iron loss characteristic of an actual machine is excellent. However, in the case of the iron core of a small generator or the EI core which is a small transformer, when the magnetic flux flowing inside the steel plate is complicated, there is a problem that the _{W17 / 50} value of the material does not match the iron loss characteristic of the actual machine. . In recent years, with the progress of the energy crisis, reduction of energy wasted in transformers has been required, and while efforts have been made to reduce iron loss in actual equipment, as described above, W _17/50 The inability to make a valid material evaluation has often led to difficulties in selecting materials.

In general, methods for reducing iron loss of a material include a method of increasing electric resistance by containing Si effective for reducing eddy current loss, a method of reducing the thickness of a steel sheet, and a method of reducing a crystal grain size. Further, there is known a method of improving the magnetic flux density by increasing the degree of integration of the crystal orientation. Among them, the method of improving the magnetic flux density has been well studied so far,
For example, in Japanese Patent Publication No. 51-2290, Al is added as an inhibitor component to steel, and slab heating is performed at a high temperature of 1300 ° C. or more, and hot finish rolling is performed at a high temperature for a short time at 980 ° C.
The technology to end hot rolling at the above temperature
No. 46-23820, Al is added to steel, after hot rolling,
1000-1200 After precipitating fine AlN hot hot-rolled sheet annealing of ℃ and by quenching associated therewith, discloses a technique for performing high pressure ratio of 80% to 95%, whereby in the B ₁₀ 1.
A material having an extremely high magnetic flux density of 95T can be obtained. However, the technique of improving the magnetic flux density by aligning the crystal orientation, which has been conventionally pursued when reducing the _{W17 / 50} , is effective in improving the iron loss characteristics of the iron core and EI core of these small generators. I couldn't say.

As alternatives to the technique for improving the magnetic flux density, a method of increasing the Si content, a method of reducing the thickness of the steel sheet, and a method of reducing the crystal grain size have been studied.
Among them, the method of increasing the Si content is not preferable because excessively containing Si deteriorates the rollability and workability, so there is a limit, and the method of reducing the thickness of the steel sheet also extremely increases the production cost. There was a limit from inviting.

[0006]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned situation, and finds an index capable of properly evaluating material properties, and is required for an iron core and an EI core of a small generator. An object of the present invention is to propose an advantageous method for manufacturing a grain-oriented electrical steel sheet having excellent low magnetic field characteristics as compared with high magnetic field characteristics.

[0007]

The details of the invention will be described below. The present inventors have examined good indexes for material evaluation with respect to the iron loss of the iron core of the actual small generator and the iron loss of the EI core. As shown in Table 1, compared with the iron loss characteristics at the high magnetic field, the low magnetic field Was found to be good, that is, the value of the (W _10/50 / W _17/50 ) ratio and the characteristics of the actual machine had a good correlation. The reason for this is that, in the case of the actual machine, the distribution of magnetic flux flowing in the steel sheet is not uniform, so iron loss in a low magnetic field is more important. It is considered that the flow is improved in a direction to make the flow more uniform, and as a result, the iron loss of the actual machine is effectively reduced.

[0008]

[Table 1]

Next, when the structure of the materials a and b from which such good actual machine characteristics were obtained was investigated, it was found that the crystal structure was fine. Conventionally, although there is a knowledge that a smaller crystal grain size is more advantageous for reducing iron loss, all of them are research on _{W17 / 50} reduction of materials and reduce iron loss of EI cores and the like. To improve the characteristics of the actual machine, that is, increase W _17/50, and increase W _10/50 and W
There has been no research on how to control the production method from the viewpoint of reducing the ratio of _10/50 / W _17/50 .

[0010] In this regard, the present inventors have conducted intensive research and have found that W
_{Increase 17/50} and reduce W _10/50 , ie W
_In order to reduce the _17/50 / W _10/50 ratio, the inhibitor is finely dispersed by controlling hot rolling and subsequent hot-rolled sheet annealing, and this form is formed until secondary recrystallization at the time of finish annealing. It has been newly found that it is important not to change, and the present invention has been completed.

That is, the present invention provides a method for producing C: 0.0050 to 0.07.
0 wt%, Si: 1.50-7.0 wt%, Mn: 0.03-0.15 wt%, A
l: A molten steel having a composition containing 0.005 to 0.017 wt%, Sb: 0.0010 to 0.080 wt% and N: 0.0030 to 0.010 wt% is converted into a slab by continuous casting, and then heated to 1300 ° C or lower, and then hot-rolled. Then, after the hot-rolled sheet annealing, one or two times of cold rolling including intermediate annealing is performed to obtain a final sheet thickness, and then a decarburizing annealing and a final finishing annealing are performed in a series of steps to produce a grain-oriented electrical steel sheet. , Finish hot rolling entry side temperature: 900 ° C or more, Cumulative rolling reduction of 4 passes before finishing hot rolling:
Finish hot rolling at 90% or more, and 800-950
℃ subjected to hot rolled sheet annealing in the temperature range of the ratio P (H ₂ 0) of the steam partial pressure to hydrogen partial pressure in the further heating process and soaking process during decarburization / P (H ₂₎ to adjust the , P in the soaking process
(H ₂ 0) / P (H ₂ ) is set to less than 0.7, while P (H ₂ 0) / P (H ₂ ) in the heating process is set to a lower value than that in the soaking process. This is a method for producing a grain-oriented electrical steel sheet having excellent low magnetic field characteristics as compared to high magnetic field characteristics.

In the present invention, at least one selected from the group consisting of 0.0001 to 0.0020 wt% of B, 0.0005 to 0.0020 wt% of Ti and 0.0010 to 0.010 wt% of Nb can be further contained as a slab component.

Further, in the present invention, it is preferable to perform electromagnetic stirring during continuous casting.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, experimental results which led to the present invention will be described. Of the various slabs shown in Table 2, the slab having the component composition of A was heated to 1200 ° C.
Sheet bar thickness: 25-50mm by hot rough rolling,
Assuming that the inlet temperature of the finishing mill is 950 ° C,
The cumulative rolling reduction of the passes was changed variously, and the thickness was 2.5 mm in 7 passes. The coil was annealed at 900 ° C. for 1 min and then cold rolled to a thickness of 0.34 mm by a tandem rolling mill.
Next, after degreasing, decarburization annealing was performed at 850 ° C. for 2 minutes. At this time, P (H ₂ 0) / P (H ₂ ) in the temperature rising region was 0.30, and that in the soaking region was 0.45. Then, apply an annealing separator,
From 00 ° C. to 1050 ° C., a final finish annealing was performed in a mixed atmosphere of 25% N ₂ and 75% H ₂ , and thereafter, the temperature was raised to 1200 ° C. in an atmosphere of H ₂ alone and held for 5 hours. These coils were further subjected to an insulating coating treatment containing magnesium phosphate containing 40% of colloidal silica as a main component, and baked at 800 ° C. to obtain products.

[0015]

[Table 2]

An Epstein-sized test piece was cut out from each of the obtained products along the rolling direction, subjected to strain relief annealing at 800 ° C. for 3 hours, and then subjected to a core loss value W _{10 at} a magnetic flux density of 1.0 T and 1.7 T. _{/ 50} , W _17/50 and magnetic flux density B ₈
Was measured. Further, an EI core was manufactured by punching out an iron core for the EI core from each product, performing strain relief annealing, stacking, and winding a copper wire. FIG. 1 shows the product characteristics (Epstein characteristics and EI characteristics) at this time. As is clear from the figure, the cumulative rolling reduction of the four passes in the first stage of the finishing mill is 90%.
In the above case, the iron loss in the high magnetic field was large and the iron loss in the low magnetic field was low, and the iron loss value of EI was extremely good. Also, the feature of the crystal structure of these products is that the crystal grain size is smaller than that of the conventional production method, and is less than 4 mm, especially 1 mm.
Many fine particles having a particle size of less than 10% were found.

Next, Table 3 shows slabs A, C, and D in Table 2.
The test conditions and product characteristics when hot-rolling and hot-rolling annealing conditions were variously changed and the sheet was passed through the same manner as in the case of FIG. 1 are shown below. As is clear from Table 3, the slab heating temperature (SRT) is 1300 ° C or less, the finish rolling entry temperature (FET) is 900 ° C or more, the rolling reduction of the four passes before finishing is 90% or more, and the hot rolled sheet annealing temperature is Only when each condition of 800 to 950 ° C. is satisfied, the iron loss in the high magnetic field is large, the iron loss in the low magnetic field is low, and the characteristics of the EI core are good.

[0018]

[Table 3]

Then, the reason why good EI characteristics were obtained in the above-described case will be described below, based on various studies. First, the method of depositing AlN as an inhibitor is novel, and it can be extremely finely and uniformly dispersed. This makes 1mm
It is considered that secondary recrystallization was able to be stably generated while having less than the crystal grains. As disclosed in Japanese Patent Publication No. 46-23820, the conventional method of precipitating AlN is to make AlN into a solid solution state in hot-rolled sheet annealing and re-precipitate in the cooling process of hot-rolled sheet annealing. This is a method of controlling the precipitation size of AlN by controlling the cold rolling speed at that time. In contrast, good results were obtained in this experiment
The method of precipitating AlN is a novel method of keeping AlN in a solid solution state until hot rolling, and precipitating AlN in the temperature rising process of hot-rolled sheet annealing.

In this method, in order to precipitate AlN finely, in order to reduce the solubility product of AlN, the Al content is made lower than the conventional preferable value, the AlN precipitation temperature is lowered, and the hot rolling process is performed. It is necessary to suppress the precipitation of AlN by hot rolling by making the finish rolling start temperature at 900 ° C. or higher and increasing the rolling reduction as high as possible. For hot-rolled sheet annealing, 1150 ° C
The conventional high temperature aimed at solid solution of AlN is rather harmful, and in order to suppress the Ostwald growth of fine AlN precipitated in the temperature rise process, the conventional annealing temperature of 950 ° C or less is completely incompatible. The result was that the hot-rolled sheet annealing at an extremely low temperature, which had been performed, was suitable. In addition, it has been found that the addition of Sb is effective for the precipitation of fine AlN during such a heating process, and increases the number of precipitation nuclei. This is considered to be because the grain boundary segregation of Sb suppresses the grain boundary precipitation of AlN.

A second innovative technique involves improving the structure of primary recrystallized grains necessary for secondary recrystallization.
Conventionally, it is known that the size of the primary recrystallized grains consumed by the silkworm is preferably uniformly small for rapid growth of the secondary recrystallized grains. Here, it is well known that the cause of the increase in the size of the primary recrystallized grains and the increase in the non-uniformity are caused by coarsening of the crystal grains before hot rolling or cold rolling. However, prior to hot rolling, it is necessary to perform high-temperature slab heating to form a solid solution of the inhibitor, and accordingly, the crystal grain size before hot rolling naturally increases. In addition, the hot-rolled sheet annealing must be performed at a high temperature for the solid solution of the inhibitor, and the crystal grain size before cold rolling naturally increases with this treatment. Therefore, when the inhibitor has a weak grain growth suppressing power, the primary particle size naturally increases.
As shown in Japanese Patent Publication No. 61, it was as coarse as 18 to 35 μm.

Also in these respects, the conditions under which good results were obtained in this experiment were the slab heating temperature at a low temperature of around 1200 ° C. and the hot-rolled sheet annealing at a low temperature of around 900 ° C. It is a perfect condition to suppress the growth of crystal grains before cold rolling and to refine and homogenize the primary recrystallization structure.
This is a revolutionary technology.

Further, from the viewpoint that the crystal grains before hot rolling are not coarsened, it is more effective that the steel has a fine cast structure. For that purpose, for example, a method of performing electromagnetic stirring during continuous casting to suppress the development of columnar crystals has a great effect. From this viewpoint, a method of directly rolling the slab after casting without heating is also preferable.

Next, the slab A shown in Table 2 above was
After heating to 950 ° C., hot rolling was performed under the conditions of FET: 950 ° C., 4-pass cumulative rolling reduction before finish rolling: 92%, and then 900 ° C.
After hot-rolled sheet annealing for 1 minute, pickling, cold rolling to a thickness of 0.34 mm with a cold tandem rolling mill, degreasing, and decarburizing annealing under various atmosphere conditions shown in Table 4. Then, after applying an annealing separator to these coils,
In a mixed atmosphere of 25% N ₂ and 75% H ₂ up to 50 ° C., the subsequent H ₂
The temperature was raised to 1200 ° C. in a single atmosphere, and final finishing annealing was performed for 5 hours. These coils are
An insulating coating containing magnesium phosphate containing 40% colloidal silica as a main component was applied and baked at 800 ° C. to obtain a product.

A specimen of Epstein size was cut out from each of the obtained products along the rolling direction, subjected to strain relief annealing at 800 ° C. for 3 hours, and then subjected to _iron loss _values W _10/50 , W _17/50 and magnetic flux. density B ₈ were measured. Furthermore, an EI core is punched out of each product, and after the strain relief annealing, an EI core is manufactured.
The actual machine iron loss was measured. The results thus obtained are also shown in Table 4.

[0026]

[Table 4]

As is clear from the table, P (H ₂ 0) / P (H ₂ ) in the heating process of the decarburizing annealing is set lower than that in the soaking process, and P (H ₂ 0) / P (H ₂ )
It can be seen that when the ratio is less than 0.7, the characteristics in the low magnetic field are better than those in the high magnetic field, and the EI characteristics are good.

The mechanism for improving such magnetic properties is considered as follows. As described above, the point of the present invention is to stabilize the secondary recrystallization by uniformly and finely depositing the inhibitor AlN in the process of raising the temperature of the norma, and to allow secondary grains of less than 1 mm to be appropriately present. Therefore, the fact that the precipitation form of AlN having uniform and fine and moderate inhibitor strength changes in the temperature rising process of decarburizing annealing or finish annealing is necessary to balance the primary particle size and the inhibitor strength in the secondary recrystallization. As a result, the secondary grain morphology is changed, and the magnetic properties particularly in a low magnetic field are deteriorated.

The atmosphere during the decarburizing annealing affects the structure of the subscale on the surface of the steel sheet, which affects the formation of forsterite during the final annealing. If the formation of this forsterite is non-uniform, the protection against the atmosphere during the finish annealing is deteriorated, causing the decomposition of AlN by additional oxidation or promoting the nitridation, and the morphological distribution of AlN is reduced. And the secondary recrystallization behavior changes. In this regard,
As in the present invention, if the atmosphere oxidizing property in the heating process of decarburization annealing is reduced, the sub-scale generated in the heating process will increase the protection of the sub-scale generated in the soaking process. It is considered that the stellite can be homogenized and secondary recrystallization can occur while maintaining the AlN morphology optimally. Thus, the present invention controls the hot-rolling conditions, deposits AlN finely during the heating process of hot-rolled sheet annealing, and decarburizes this form until the subsequent secondary recrystallization to freeze this form. It is based on a completely new technical idea of controlling the annealing conditions.

Next, the reasons for limiting each component of the present invention will be described. First, the reason why the component composition of the material is limited to the above range will be described. C: 0.0050 to 0.070 wt% If the C content exceeds 0.070 wt%, the amount of γ transformation becomes excessive, the distribution of Al during hot rolling becomes non-uniform, and AlN precipitates during the heating process of hot-rolled sheet annealing. Is not uniform, and good magnetic properties cannot be obtained in a low magnetic field. On the other hand, 0.00
If it is less than 50% by weight, the effect of improving the structure cannot be obtained and the secondary recrystallization becomes incomplete, which also leads to the deterioration of the magnetic properties. Therefore,
C was limited to the range of 0.0050 to 0.070 wt%.

Si: 1.50 to 7.0 wt% Si is an essential element for increasing electric resistance and reducing iron loss. For this purpose, it is necessary to contain 1.50 wt% or more. %, The workability deteriorates,
It is extremely difficult to manufacture and process the product.
Limited to the wt% range.

Mn: 0.03 to 0.15 wt% Mn is also an element necessary for increasing electric resistance and improving hot workability at the time of production. For this purpose, a content of 0.03 wt% or more is necessary. However, if the content exceeds 0.15 wt%, γ transformation is induced and magnetic properties are deteriorated. Limited.

Al: 0.005 to 0.017 wt% In addition to the above elements, the steel must contain an inhibitor component for inducing secondary recrystallization. Therefore, Al is contained as an inhibitor component in an amount of 0.005 to 0.017 wt%. Content within the range. Here, if the Al content is less than 0.005 wt%, the amount of AlN precipitated during the heating process in hot-rolled sheet annealing is insufficient, and if it exceeds 0.017 wt%, the slab at around 1200 ° C is used. It becomes difficult to form a solid solution of AlN at low temperature heating, and the solid solution temperature of AlN rises, so that AlN precipitates in hot rolling, and it becomes impossible to finely precipitate AlN in a heating process of hot-rolled sheet annealing. Good iron loss characteristics in a low magnetic field cannot be obtained. Therefore, Al was contained in the range of 0.005 to 0.017 wt%. In addition, when slab heating is performed at a high temperature of about 1400 ° C. to eliminate the above deficiencies, the crystal grain size of the product becomes coarse, iron loss in a high magnetic field is reduced, and iron loss in a low magnetic field is reduced. As a result, the iron loss of the actual machine deteriorates.

Sb: 0.0010-0.080 wt% Sb promotes fine precipitation of AlN in the grains by segregating at the grain boundaries, and is nitrided by the time of secondary recrystallization.
It is a useful element that suppresses the change of AlN form. However, if it is less than 0.0010, its effect is poor. On the other hand, if it exceeds 0.080 wt%, mechanical properties such as bend characteristics of the product are deteriorated.
The content was set in the range of 10 to 0.080 wt%.

N: 0.0030 to 0.010 wt% Since N is a component constituting AlN, it must be contained in an amount of 0.0030 wt% or more. However, if the content exceeds 0.010 wt%, it gasifies in the steel and causes defects such as blisters, so the content is limited to the range of 0.0030 to 0.010 wt%.

B: 0.0001 to 0.0020 wt%, Ti: 0.0005 to 0.
0020 wt%, Nb: 0.0010-0.010 wt% B, Ti and Nb all form fine precipitates in hot rolling, and are used in the subsequent process of raising the temperature of hot-rolled sheet annealing.
Since it has the effect of increasing the precipitation nuclei of AlN, it is contained as necessary. In order to obtain such an effect, the content of B is 0.0001% by weight or more, the content of Ti is 0.0005% by weight or more,
Requires a content of 0.0010 wt% or more. However, if the content of B exceeds 0.0020 wt%, Ti
If the content exceeds 0.0020 wt% in Nb, and if the content exceeds 0.010 wt% in Nb, the mechanical properties such as the bend characteristics of the product will be deteriorated. is there.

As for other elements, Sn and Cr
Has a function similar to that of Sb and can be added to steel at any time, and a preferable amount for this is 0.0010 to 0.30 wt%. Since addition of Mo and the like has the effect of improving the surface properties of the steel sheet, it can be appropriately contained.

Next, the reasons for limiting the manufacturing conditions will be described. Slab heating temperature: 1300 ° C or less When slab heating is performed at a temperature exceeding 1300 ° C, fine grains of 1 mm or less in product crystal grains decrease and coarse grains increase, resulting in deterioration of iron loss in a low magnetic field. . Therefore, in order to obtain good crystal grain distribution and low magnetic field characteristics, the slab heating temperature must be 13
It is necessary to be lower than 00 ° C. Furthermore, in recent years, a method of performing direct hot rolling after continuous casting without performing slab heating has been developed, but since this method does not increase the slab temperature,
It can be said that this method is suitable for the method of the present invention.

Temperature of finishing hot-rolling side: 900 ° C. or more If the temperature of finishing hot-rolling side is lower than 900 ° C., precipitation of AlN occurs during finish rolling and magnetic properties are deteriorated. Must be at least 900 ° C.

Cumulative rolling reduction of 4 passes before finishing hot rolling: 90%
Although the finish rolling is usually performed in 4 to 10 passes, according to the present invention, as shown in FIG. 1, when the cumulative rolling reduction in the preceding 4 passes is 90% or more, the precipitation of AlN during the finish rolling is reduced. Since the low magnetic field characteristics are not improved and the low magnetic field characteristics are improved, the cumulative rolling reduction of the four passes before the finishing hot rolling is specified to be 90% or more. The finish hot-rolling temperature (FDT) is not particularly specified, but if it is lower than 750 ° C, it becomes difficult to perform rolling.
The above is preferred. Also, the winding temperature (CT) is not particularly specified, but if the temperature is lower than 500 ° C, the winding property deteriorates.
Advantageously, it is above 500 ° C.

Hot rolled sheet annealing temperature: 800 to 950 ° C. By the above-described controlled rolling, hot rolled sheet annealing is performed on a hot rolled coil in which AlN precipitation is suppressed during hot rolling. The point of the present invention is that the operation is performed at an extremely low temperature as compared with the related art. Here, the annealing temperature is 800 ℃
If the temperature is lower than 950 ° C., fine precipitation of AlN during the heating process becomes insufficient.
Since the secondary recrystallization becomes unstable and the magnetic properties deteriorate, the annealing of the hot-rolled sheet was performed at a temperature in the range of 800 to 950 ° C.

Then, cold rolling is performed once or twice including intermediate annealing to finish to a final thickness. At this time, the cold rolling may be tandem rolling or sendzimer rolling, but tandem rolling is preferable from the viewpoint of productivity.

P (H ₂ 0) / P (H ₂ ) in the soaking process: less than 0.7 P (H ₂ 0) / P (H ₂ ) in the heating process: a value lower than that in the soaking process Decarburizing annealing following cold rolling is also an important point. P (H ₂ 0) / P (H ₂ ) in the soaking process is 0.7
Above this, a beautiful glossy and uniform gray forsterite film cannot be obtained, and good magnetic properties cannot be obtained. Also, if P (H ₂ 0) / P (H ₂ ) in the heating process is higher than that in the soaking process, the protection by the forsterite at the time of finish annealing is deteriorated, and the inhibitor before secondary recrystallization. Since the morphology changes and a sufficient amount of secondary particles of 1 mm or less cannot be obtained, the low magnetic field characteristics deteriorate. For this reason, P (H ₂₀ ) / P (H ₂ ) in the heating process is set lower (preferably 0.05 or more) than that in the soaking process, and P (H ₂₀ ) / P (H (H)) in the soaking process. ₂ ) was limited to less than 0.7 (preferably 0.3 or more).

After that, after applying an annealing separating agent, a final finishing annealing is performed to perform secondary recrystallization. In the final finish annealing, it is preferable to raise the temperature to a high temperature of about 1200 ° C. so as to purify and form a forsterite base coat. Thereafter, the steel sheet surface is coated with an insulating coating to obtain a product, but the steel sheet surface may be subjected to a mirror finishing treatment before and after the coating. Further, a tension coating may be used as the insulating coating.

[0045]

【Example】

Example 1 Molten steel having the component composition of A to M shown in Table 2 above was formed into a slab by continuous casting while being electromagnetically stirred, heated to 1180 ° C, formed into a 45 mm thick sheet bar with five coarse passes, and FET: 950.
The sample was hot-rolled at 2.2 ° C. to a thickness of 2.2 mm by 7-pass finishing hot rolling. At that time, the cumulative draft of the four passes before finishing was set to 93%. Then, the obtained hot coil was annealed at 900 ° C. for 1 minute, and then cold rolled to a thickness of 0.34 mm by a tandem rolling mill. Then, decarburization annealing was performed. At that time, P (H ₂₀ ) / P (H ₂ ) in the temperature raising process was set to 0.45, and that in the soaking process was set to 0.50, and annealing was performed at 820 ° C. Thereafter, after applying an annealing separator, the temperature is raised in an atmosphere of N ₂ alone up to 700 ° C., then in a mixed atmosphere of 25% N ₂ and 75% H ₂ up to 950 ° C., and thereafter H ₂ After the temperature was raised to 1100 ° C. in a single atmosphere, final finishing annealing was performed for 5 hours. Thereafter, an insulating coating was applied to obtain a product.

An Epstein test piece and an iron core for an EI core were punched from each of the obtained product plates, and the iron loss characteristics thereof were evaluated. Table 5 shows the obtained results. As is clear from the table, the grain-oriented electrical steel sheet obtained according to the present invention was excellent in iron loss characteristics in a low magnetic field as compared with high magnetic field characteristics, and also had good iron loss in an actual machine.

[0047]

[Table 5]

Example 2 In Table 2, molten steel having a composition of H was formed into a slab by continuous casting while being electromagnetically stirred, heated to 1230 ° C., and then subjected to 45 coarse passes in 5 passes.
The sheet bar was formed into a sheet bar having a thickness of 2 mm, and the FET was hot-rolled to a thickness of 2.1 mm at 930 ° C. by 6-pass finishing hot rolling. At that time, the cumulative draft of the four passes before the finishing was varied in various ways. Then, the obtained hot rolled coil was annealed at 900 ° C. for 1 min.
It was cold rolled to a thickness of 0.26 mm by a tandem rolling mill. Next, in performing decarburization annealing, P (H ₂ 0) / P (H
₂ ) and that of the soaking process were variously changed, and annealing was performed at 820 ° C. Then, apply an annealing separator, and then
Until ° C. in an atmosphere of N ₂ alone, then up to 950 ° C. 25%
In a mixed atmosphere of N ₂ and 75% H _{2, then in} an atmosphere of H ₂ alone
After the temperature was raised to 1080 ° C., final finishing annealing was performed for 5 hours. Thereafter, an insulating coating was applied to obtain a product.

An Epstein test piece and an iron core for an EI core were punched from the obtained product plate, and the iron loss characteristics thereof were evaluated. Table 6 shows the obtained results. As is clear from the table, the grain-oriented electrical steel sheet obtained according to the present invention method is superior in iron loss characteristics in a low magnetic field as compared with high magnetic field characteristics,
The iron loss of the actual machine was also good.

[0050]

[Table 6]

Example 3 In Table 2, the molten steel having the composition of F was formed into a slab by continuous casting while being electromagnetically stirred, heated to 1180 ° C., and then 45 mm in five coarse passes.
After forming a thick sheet bar, the FET was hot-rolled to a thickness of 2.4 mm at 950 ° C. by 6-pass finishing hot rolling. At that time, the cumulative draft of the four passes before the finishing was varied in various ways. Then
The obtained hot-rolled coil was annealed at 900 ° C. for 1 min and then cold-rolled to a thickness of 0.49 mm by a tandem rolling mill. Next, in performing decarburization annealing, P (H ₂ 0) / P
(H ₂ ) and that of the soaking process were variously changed, and annealing was performed at 840 ° C. Then, apply an annealing separator, and then
In an atmosphere of N ₂ alone up to ℃, then 25% up to 1000 ℃
In a mixed atmosphere of N ₂ and 75% H _{2, then in} an atmosphere of H ₂ alone
After the temperature was raised to 1150 ° C., final finishing annealing was performed for 5 hours. Thereafter, an insulating coating was applied to obtain a product.

An Epstein test piece and an iron core for an EI core were punched from the obtained product plate, and their iron loss characteristics were evaluated. Table 7 shows the obtained results.

[0053]

[Table 7]

As is clear from the table, the grain-oriented electrical steel sheet obtained according to the present invention is superior in iron loss characteristics in a low magnetic field as compared with high magnetic field characteristics, and has good iron loss in an actual machine. Met.

Thus, according to the present invention, it is possible to obtain a grain-oriented electrical steel sheet which is more excellent in iron loss characteristics in a low magnetic field than in a high magnetic field characteristic, and is also excellent in iron loss characteristics of an actual machine.
It is particularly effective when used in applications such as small generator iron cores and EI cores.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a graph showing a relationship between a cumulative _rolling reduction of four passes in a first stage of finishing hot _rolling , a material (W _10/50 / W _17/50 ), and an actual iron loss W _17/50 of an EI core. It is.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenichi Sadahiro 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. Chome (without address) Inside Kawasaki Steel Corporation Mizushima Works

Claims (3)

[Claims] 1. C: 0.0050 to 0.070 wt%, Si: 1.50 to 7.0 wt%, Mn: 0.03 to 0.15 wt%, Al: 0.005 to 0.017 wt%, Sb: 0.0010 to 0.080 wt%, and N: 0.0030 to 0.010 wt% wt%
Slab by continuous casting, and then heated to 1300 ° C or lower, hot-rolled, and after hot-rolled sheet annealing, finalized by cold rolling twice, including once or intermediate annealing After manufacturing the grain-oriented electrical steel sheet through a series of steps of decarburizing annealing followed by final finish annealing after the sheet thickness is reached, the finishing hot-rolling side temperature: 900 ° C or more, and the cumulative rolling reduction of 4 passes before finishing hot rolling: Finish hot rolling at 90% or more, hot-rolled sheet annealing in the temperature range of 800 to 950 ° C, and the partial pressure of steam with respect to the hydrogen partial pressure in the heating and soaking processes during decarburization annealing While adjusting the ratio P (H ₂ 0) / P (H ₂ ) to make P (H ₂ 0) / P (H ₂ ) less than 0.7 in the soaking process,
P (H ₂ 0) / P (H ₂ ) in the heating process is set to a lower value than that in the soaking process. Directivity superior to low magnetic field characteristics compared to high magnetic field characteristics. Manufacturing method of electrical steel sheet. 2. The slab according to claim 1, further comprising: B: 0.0001 to 0.0020 wt%, Ti: 0.0005 to 0.0020 wt%, and Nb: 0.0010 to 0.010 wt%.
A method for producing a grain-oriented electrical steel sheet having excellent low magnetic field characteristics as compared with high magnetic field characteristics, characterized in that the composition contains at least one selected from the group consisting of: 3. The method for producing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein electromagnetic stirring is performed during continuous casting.